Casters are extensively used to support and effect movement of a wide variety of objects, including carts, dollies, portable trucks and machines, and furniture. They handle static and dynamic loads on a wide variety of surfaces, such as wooden floors, rug covered floors, hard packed earth, concrete pavement, etc. For their size and weight, the loads casters handle are relatively large.
Presently available casters use kingpins or ball bearings between welded plates to handle the stress and strain imposed by these loads. Kingpins, however, are subject to fracture and shearing which results in premature replacement of casters that are otherwise undamaged. Welded plates with ball bearings therebetween, on the other hand, are more complex to manufacture, and are relatively difficult to repair, necessitating costly replacement of the caster. Also, the ball bearings are somewhat exposed to undesirable grit, dust, grease, etc., which accelerates wear and decreases their efficiency.
In producing casters, moreover, it is relatively costly to manufacture a line of swivel type casters (wheel both rotates in direction of and revolves about its axis) and another line of non-swivel type casters (wheel only rotates). Efforts, to date, to economically manufacture essentially interchangeable swivel and non-swivel types of casters have not been completely successful.
Other problems encountered with available casters are that they tend to corrode or to become clogged with filamentary materials or contaminated with dirt, grease, debris, etc. For example, in a warehouse storing textiles, filamentary materials, such as rug fibers, tend to be picked up by the caster and become lodged between the wheel and axle resulting in a jamming of the caster. In spite of many years during which casters have been used, and in spite of the many different designs of casters, the clogging by filamentary materials is still a major cause of caster malfunction. There also has been a long subsisting concern about casters for sanitary applications, such as hospitals, cafeterias and restaurants. Generally available casters, because of their construction, continue to tend to pick up and hold dirt, debris and other contaminants, as well as rust and corrode.
Thus, there is a need for new and improved casters which are not beset with these drawbacks.